The invention relates to a system and method for detecting an air leak in an exhaust system coupled to an engine.
To meet current emission regulations, automotive vehicles must regulate the air-fuel ratio supplied to the vehicles"" engine cylinders to achieve maximum efficiency of exhaust gas catalysts. For this purpose, it is known to control the air-fuel ratio of an internal combustion engine using an exhaust gas oxygen sensor positioned in the exhaust stream from the engine. The exhaust gas sensor provides feedback data to an electronic controller that calculates desired air-fuel ratio values over time to achieve optimum efficiency of the catalyst in the exhaust system.
When an air leak occurs in an exhaust system upstream of an exhaust gas sensor, atmospheric air may be inducted into the exhaust system during idle or deceleration operating conditions. As a result, the exhaust gas sensor may indicate a lean air-fuel ratio even though a combusted air-fuel mixture in an engine cylinder was not a lean mixture. An electronic engine controller utilizing the inaccurate air-fuel ratio measurement may not be able to maintain an optimal air-fuel ratio for optimal catalyst efficiency. Thus, air leaks in the exhaust system may result in increased emissions and decreased fuel economy.
A known engine control system detects air leaks in an exhaust system by measuring the number of switch transitions in an output signal of an oxygen sensor disposed upstream of an emission catalyst. However, the known system relies only the instantaneous oxygen sensor signals and not on any other engine air-fuel control parameters. Thus, the known system may incorrectly indicate air leaks in the exhaust system during relatively short transient operation of the oxygen sensor when no air leak actually exists.
The inventors herein have thus recognized that there is a need for a more accurate system and method for detecting an air leak within an exhaust system coupled to an engine.
The foregoing problems and disadvantages are overcome by a system and method for detecting an air leak within an exhaust system.
The method for detecting an air leak within an exhaust system includes measuring an exhaust gas constituent in exhaust gases from the engine when the engine is operating in an idle operating mode. The method further includes determining when the air leak is present in the exhaust system based on a level of the measured exhaust gas constituent, a first air-fuel correction value, and a second air-fuel correction value.
A system for detecting an air leak within an exhaust system is also provided. The system includes a first sensor generating a first signal indicative of a mass air flow or a pressure in the intake manifold. The system further includes a second sensor generating a second signal indicative of an engine speed. The system further includes a third sensor generating a third signal indicative of an air-fuel ratio in exhaust gases from the engine. Finally, the system includes a controller operably connected to the first, second, and third sensors. The controller is configured to determine when the engine is operating in an idle operating mode based on the first and second signals. The controller is further configured to determine whether the air leak is present in the exhaust system based on the third signal, a first air-fuel correction value, and a second air-fuel correction value.
The inventive system and method provides a substantial advantage over known systems and methods. In particular, the system and method can more accurately detect air leaks in exhaust system by utilizing two air-fuel correction values in conjunction with an exhaust gas sensor signal.